This invention relates generally to a method and apparatus for facilitating access to the mold halves of a molding machine. More particularly, the invention relates to a method and apparatus for releasing and at least partially retracting a tie rod from the zone between opposed movable and stationary platens of a molding machine.
A great many products are today manufactured using suitable molding methods and apparatus. A number of different methods have been developed in this regard including blow, extrusion, and injection molding. Many of the molding machines used in connection with these methods entail opposed stationary and movable platens and opposed mold halves disposed on and between these platens. Often a number of tie rods extend from a portion of the frame of the molding machine through the movable platen to the stationary platen. The movable platen is normally translated toward and away from the stationary platen to abut and separate the mold halves in the course of a molding cycle and the tie rods thus support and guide the movable platen as it is slidingly translated therealong.
Each set of mold halves disposed on and between the platens is normally suited for the manufacture of objects of only a particular size and type. Thus, when sufficient numbers of these objects have been manufactured, the mold halves must be removed and a different set installed to permit the manufacture of different objects. Since the mold halves are normally fastened to the platens, a number of problems occur in connection with the removal and installation of mold halves. One rather troublesome problem concerns the accessability of the molds when tie rods extend between the platens.
Tie rods extending between the stationary and movable platens may obstruct the removal of installation of mold halves by restricting either the accessability of the portions of the mold halves connected to the platens or the movement of the mold halves in the area of the platens prior to connection therewith. This problem may become particularly acute if the mold halves being removed or installed are either large relative to the space available between the tie rods or irregularly shaped.
One approach to the problem presented above has been to remove from between the platens one or more of several essentially permanent tie rods. However, because of the nature of the connections of the tie rods to the molding machine and the size of the tie rods, this may present a rather formidable task, Because the tie rods must often resist large forces during the molding process, they may be quite large and may be connected to the stationary platen and frame of the molding machine by large, heavy-duty connections. Removal of one or more of these tie rods at best entails removal of certain of these large connections and movement of the large tie rods. Once the molds are removed and a different set installed, the tie rods and connections must, of course, be replaced.
As suggested in the preceding paragraph, one of the problems which must be confronted in the removal of a tie rod from between the platens resides in the nature of the connection of the tie rod to the molding machine. Often relatively large longitudinal forces are exerted on the tie rods during the molding operations. The connections of the tie rods to the molding machine should be capable of resisting these forces; however, if a tie rod is to be conveniently removed from between the platens, the connection should be readily removable. From a design standpoint, these two requirements may conflict. The result has been that many connections of tie rods of the molding machine appearing in the prior art may not satisfactorily meet these criteria.
Another difficulty which may occur in the course of removing a tie rod between the platens of a molding machine and then replacing it, resides in the supervision and control of the movement of the tie rod when disconnected from the molding machine. This may be a particular problem in the case of an automated process entailing the longitudinal retraction and reextension of a tie rod between the platens. If retraction of the tie rod is not carefully supervised and controlled, during removal from between the platens, the tie rod and/or molding machine may be damaged due to over retraction of the tie rod. Similarly, if reextension of the tie rod back into an operating position between the platens is not carefully supervised and controlled, the tie rod and/or molding machine may be damaged or the tie rod may not be properly positioned to be reconnected to the molding machine.